The present invention is directed toward generating control signals for use in the control of wheel slip for vehicles. Cross-referenced U.S. Pat. No. 3,827,760 issued on Aug. 6, 1974 in the name of the present applicant, discloses a signal processing circuit for a wheel slip control system in which an output control signal is generated when the deceleration exceeds a variable reference increment of wheel speed. The variable reference increment of wheel speed was directly related to the rate of change of wheel speed.